English to German Law/Patents Law: Contract(s)

Es geht mir im Prinzip um die Bezüge in Satz (i), d.h. worauf bezieht sich jeweils their und they?

Furthermore, an exception pertains to institutions that perform their activities primarily or exclusively within a restricted circle. This exception applies to (i) persons who perform brokerage services exclusively for the undertaking of which they are a subsidiary, for their subsidiaries or for another subsidiary or undertaking of which they are a subsidiary, (ii) persons whose services consist exclusively of the management, on the basis of an agreement with an employer, of an employees- participation plan in respect of securities issued for the employer's account; and (iii) persons whose services consist exclusively of the performance of both the services referred to under (i) and (ii).